In recent years, a so-called inkjet method using an inkjet head has been widely employed in a case of performing printing using ink on a print medium such as paper, in a case of forming an orientation film or applying UV ink onto a substrate (transparent substrate) of a liquid crystal display device or the like, or in a case of applying a color filter onto a substrate of an organic EL display device.
For example, JP 3073493 B discloses an inkjet head including line-type inkjet nozzles in which nozzles are arranged in a row. JP 3073493 B also discloses a technology of improving a process speed for coating a liquid material by devising arrangement of the line-type inkjet nozzles as shown in FIGS. 5 to 7 of JP 3073493 B (Patent Document 1).
Further, JP 09-138410 A discloses an inkjet head for forming a film with a uniform thickness, in which nozzles are arranged in a plurality of rows and in a plurality of columns in a predetermined area, and inkjet nozzles in an arbitrary row are arranged by being shifted by a half pitch with respect to the arrangement of nozzles in an adjacent row. JP 09-138410 A also discloses a technology of coating a liquid material while moving, in a zig-zag manner, the line-type inkjet nozzles including nozzles that eject the liquid material and are arranged in series, to thereby form a film with a uniform thickness (Patent Document 2).
Further, as an example of a device for detecting an ejection abnormality of an inkjet head, JP 05-149769 A discloses a technology of picking up an image of a flying liquid droplet which is ejected from the inkjet head, from a direction orthogonal to a direction in which the liquid droplet flies, and integrating the flying image with respect to a central axis of the liquid droplet, assuming that the liquid droplet has a rotationally symmetrical shape with respect to a central axis of the flying direction, thereby calculating a volume of the liquid droplet (Patent Document 3).
Further, JP11-227172A discloses a technology of picking up an image of a liquid droplet ejected from the inkjet head a plurality of times by providing time differences, and measuring a droplet velocity of the liquid droplet based on positional differences and the time differences between a plurality of taken images of the liquid droplet (Patent Document 4).
Further, JP2001-322295A discloses a method of applying light at the time of photographing, and also discloses a technology in which a light source and image taking means are arranged so as to face a scattering plate, and a liquid droplet which is an object to be measured is positioned among the light source, the image taking means, and the scattering plate, and light irradiated from the light source is scattered by the scattering plate, thereby picking up an image of the liquid droplet by the image taking means (Patent Document 5).
On the other hand, manufacturing processes for a liquid crystal display device include a process of forming an orientation film on a transparent substrate. The orientation film is used for controlling a liquid crystal orientation, and an orientation film material such as polyimide is coated and formed on the substrate to thereby form the orientation film.
As an orientation film coating forming method, a flexographic printing method using a flexographic printing apparatus is generally employed. However, in recent years, a method of forming an orientation film on a transparent substrate by using a print head, that is, the so-called inkjet method is proposed (see Patent Documents 6 and 7).
In the case of the flexographic printing method, pattern formation of the orientation film can be easily performed and higher productivity is obtained, whereas the method has the following problems. That is: for example, (1) a failure that the orientation film material is not coated on the transparent substrate repeatedly occurs in a case where dust is attached to a surface of a relief printing plate; (2) usage of the orientation film material is large in amount; (3) a recovery time becomes longer and operating rates of the apparatus are lowered because cleaning for an anilox roll, a relief printing plate, or the like is necessary in a case where the apparatus is stopped due to a trouble or the like; and (4) coating with respect to a substrate with large irregularities or a substrate having a curved surface cannot be performed.
The inkjet method enables solving those problems inherent in the flexographic printing method, and obtainment of a stable film quality. An inkjet printer used for the inkjet printing method includes a movable print head unit. In general, the print head unit has about 1 to 6 (4 in FIG. 22) print heads mounted thereto as illustrated in FIG. 22. The print head unit reciprocates in a width direction of the transparent substrate in a direction of 90° (vertically in FIG. 22) with respect to an advancing direction (rightwardly in FIG. 22) of the transparent substrate which is a material to be coated. In synchronization with the reciprocation, the transparent substrate is intermittently moved in an advancing direction (longitudinal direction), thereby forming the orientation film on the transparent substrate.
[Patent Document 1] JP 3073493 B (FIGS. 5 to 7)
[Patent Document 2] JP 09-138410 A (FIGS. 1, 4, and 5)
[Patent Document 3] JP 05-149769 A
[Patent Document 4] JP 11-227172 A
[Patent Document 5] JP 2001-322295 A
[Patent Document 6] JP 03-249623 A
[Patent Document 7] JP 07-092468 A